1. Field of the Invention
The invention relates to seat assemblies for motor vehicles. More particularly, the invention relates to a seat back having an inner seat back independently movable with respect to an outer seat back.
2. Description of the Related Art
A motor vehicle includes at least one seat assembly for supporting an occupant within a passenger compartment of the motor vehicle. The seat assembly includes a seat cushion and a seat back for supporting the torso of an occupant seated on the seat cushion. Typically, the seat back is pivotable relative to the seat cushion between a plurality of seating positions. Further, the seat assembly is typically mounted to a floor mounted seat adjuster that allows horizontal and vertical comfort adjustment of the seat cushion and seat back together relative to the floor of the vehicle.
Some seat assembly designs, commonly referred to as “All Belt to Seat” (ABTS) designs, include belt restraint devices incorporated into the seat structure. Vehicle manufacturers desire ABTS designs for a variety of reasons, such as reduced complexity in the assembly of the vehicle, improved comfort due to the more proximal location of the belt exit point relative to the occupant, and packaging concerns related to a particular vehicle design.
The seat back in a conventional ABTS design typically includes at least one reinforced side member that bears the majority of the forces or “belt loads” associated with the restraint device. Due to the potential magnitude of the belt loads, the reinforced side member is coupled directly to the horizontal rails of the seat adjuster. As a result, the seat back in a conventional ABTS design is not vertically adjustable with the seat cushion.
It, therefore, remains desirable to provide an ABTS design having a seat back, or at least a portion thereof, vertically adjustable with the seat cushion especially to provide proper lumbar support in the vertical axis.